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what 6mm

 
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  #36  
Old 03-29-2013, 10:50 AM
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Re: what 6mm

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Originally Posted by CB11WYO View Post
I need to mention though, concerning the recoil comments... My 6x47 does weigh 13 lbs. I'm thinkin somethin to do with the 30" Lilja But then again I never needed it to be a pack-on-foot-all-day-long kind of gun.
with that case capacity, you really don't need that long of a barrel. Even a 26" barrel is almost too long. I'd look at a 24" barrel. I mean you looking at a case that is about 1.85" long, and that's a lot shorter than a .243, and actually a shorter body length than the 6x250. The shorter barrel in a compariable profile will be much more rigid, and probably shoot better groups. In a pinch you could probably get by OK with a 22" barrel, but the powder range will be shorter.
gary
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  #37  
Old 03-30-2013, 03:25 PM
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Re: what 6mm

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Originally Posted by Trickymissfit View Post
with that case capacity, you really don't need that long of a barrel. Even a 26" barrel is almost too long. I'd look at a 24" barrel. I mean you looking at a case that is about 1.85" long, and that's a lot shorter than a .243, and actually a shorter body length than the 6x250. The shorter barrel in a compariable profile will be much more rigid, and probably shoot better groups. In a pinch you could probably get by OK with a 22" barrel, but the powder range will be shorter.
gary
I will definitely agree the 30 incher is long as a bad dream some days. But alot of why I like it is it brings out big-boy performance from such a little case. I met a guy at the range the other day with a 24" custom .243. He was shooting 95 gr. bullets at 3000 fps. Like you said the 6x47L case is alot smaller than a .243 yet I'm pushing the same 95 grainers to 3100 fps, with less powder. Am I just naive in thinking that the better performance is coming mostly from my extra barrel length? (and of course efficient case design...)

So I guess the question you raise for me is: is there a way to get my same 30-inch-barrel performance out of a 6x47L in a 24" barrel while still using my 95 grain bullet?
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Last edited by CB11WYO; 03-30-2013 at 05:18 PM. Reason: Continuity
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  #38  
Old 03-30-2013, 03:52 PM
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Re: what 6mm

I shot the 6 Dasher in competition in a Panda action, and never had any problems forming the cases, but it does take work as far as turning the necks and fire forming. It would handle pressure better than the 6/250 as I had one of these also, though on a Rem action. My barrel was only 24.5" and gave nothing up to the big 30's at 600 yds. I shot a 108 gr bullet., and is a real pleasure to shoot in a light Varmint rifle.
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  #39  
Old 03-31-2013, 11:12 AM
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Re: what 6mm

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Originally Posted by CB11WYO View Post
I will definitely agree the 30 incher is long as a bad dream some days. But alot of why I like it is it brings out big-boy performance from such a little case. I met a guy at the range the other day with a 24" custom .243. He was shooting 95 gr. bullets at 3000 fps. Like you said the 6x47L case is alot smaller than a .243 yet I'm pushing the same 95 grainers to 3100 fps, with less powder. Am I just naive in thinking that the better performance is coming mostly from my extra barrel length? (and of course efficient case design...)

So I guess the question you raise for me is: is there a way to get my same 30-inch-barrel performance out of a 6x47L in a 24" barrel while still using my 95 grain bullet?
a .243 will push a 95 grain bullet right ontop of 3200fps using a 26" barrel. Yet the 6BR with the same bullet will go an honest 2850fps with a 24" barrel. and will probably do over 2900fps with the same barrel. The 6BR was made for a 22" barrel, and we see little gains to be made with the much longer barrels. The 250 case was also designed around the 22" barrel length, but is best with a 24" barrel for a near full powder burn. I use a 26" barrel with the 6/250AI, and honestly think it'd work well with a 24" barrel with the right powder. It will do a slight tick under 3000fps with a 105 grain bullet. So a 95 grain bullet ought to do right at 3100fps. The others have gotten 3100fps out of the same bullet in the 6x47L. That a smaller case, and we learn that it must have a very efficient powder burn like the 6BR. On the otherhand the 6mm INT. (great round) is listed by Sierra at almost 2800fps with the 105 grain bullet. (20" barrel length) I kinda think their loads are somewhat anemic here anyway, and think it has another 100fps in it. The shoulder to base length is 1.39" with an overall length of 1.91". In improved version would be very similar to the 6x47L if I have the drawings right in my head. The Ackley handbook shows two or three improved international cases, and one (or more) of them are said to push a 95 grain bullet to almost 3300fps! Barrel length is unspec'd. The HLS is also similar in velocity

The real serious issue with longer barrels (besides weight) is harmonics. They literally become a tuning fork in an effort to gain another hundred feet per second. Plus it would take a middle line backer to hump that thing a couple miles with a 1" strait contour. Lilja did a test a few years back with his #7 contour barrels. He found that a 21" barrel was 2.75 stiffer than the same contour 26" long. I did my own testing (although rather crude), and pretty confirmed his thoughts. I also got similar results with the Remington #5.5 contour (maybe 2.5 times stiffer) going from 26" to 20" in length. But the test with the Remington barrel cannot be compaired exactly with his test as part of the big end hand been cut off. I would have prefered a 22" barrel, but it just didn't come out that way. The rest of my testing would be considered flawed by any man, as there were too many other things added into the mix to compair the short barrel with the longer in performance, except for velocity. In this case I lost 74fps. (.223 case)
gary
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  #40  
Old 04-01-2013, 09:28 AM
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Re: what 6mm

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Originally Posted by Trickymissfit View Post
....
The real serious issue with longer barrels (besides weight) is harmonics. They literally become a tuning fork in an effort to gain another hundred feet per second....
gary
Gary,

I agree, and what you've said makes sense.

I'll definitely keep that in mind for future rifles. For now she seems to be shooting good enough for what I need her for, 1/3 MOA to 1000+ yards or so. So I'll probably let her be.

Thanks!
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Last edited by CB11WYO; 04-01-2013 at 09:28 AM. Reason: continuity
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  #41  
Old 04-01-2013, 10:05 AM
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Re: what 6mm

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Originally Posted by CB11WYO View Post
Gary,

I agree, and what you've said makes sense.

I'll definitely keep that in mind for future rifles. For now she seems to be shooting good enough for what I need her for, 1/3 MOA to 1000+ yards or so. So I'll probably let her be.

Thanks!
*I honestly think the improved 6mm International might just be the perfect 6mm case. Looking at the three I have some data on, one is kind of left stunned! With a 100 grain bullet in each round the Durham version does 2970fps in a 22" barrel with H380 powder. The same round with 4350 goes 3100fps! Now that round has a slightly shortened neck length (I'd guess it to be about .34") and a 40 degree shoulder with minimum taper. That round with a 24" barrel and some of our newer powders (H1000?) ought to hit the 3250fps mark. Cases can be formed from .243, .250 Sav., or even 22-250 brass as it has an overall length of 1.875". Looks like he reamed the chamber with a standard 6mmAI reamer.

*The Donaldson International starts out similar, but uses the standard taper and a 30 degree shoulder with a shorter necklength (probably about .33"). He got 3200fps with that 100 grain bullet in an unknown barrel length (4350 powder again)

* The Remington International design has a lot of taper in the case with a very long neck length (close to .37"). Walker still got 3060fps out of it! (must have been a very hot load) He used 4064 powder.

These rounds are ideal for a short action Remington (known to be a little on the short side anyway). Are extremely efficient, and from the shoulders forward are very well designed, and should have a very good barrel life. The Donaldson and Durham version are far better rounds than a Dasher. Yet similar in many ways.
gary
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  #42  
Old 04-04-2013, 07:04 PM
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Re: what 6mm

Might want to do a littel research on the 6mm compition match.
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